// 压缩图片
function compress(img, Orientation) {
    let canvas = document.createElement('canvas')
    let ctx = canvas.getContext('2d')
    //瓦片canvas
    let tCanvas = document.createElement('canvas')
    let tctx = tCanvas.getContext('2d')
    // let initSize = img.src.length;
    let width = img.width
    let height = img.height
    //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
    let ratio
    if ((ratio = (width * height) / 4000000) > 1) {
        // console.log("大于400万像素");
        ratio = Math.sqrt(ratio)
        width /= ratio
        height /= ratio
    } else {
        ratio = 1
    }
    canvas.width = width
    canvas.height = height
    //    铺底色
    ctx.fillStyle = '#fff'
    ctx.fillRect(0, 0, canvas.width, canvas.height)
    //如果图片像素大于100万则使用瓦片绘制
    let count
    if ((count = (width * height) / 1000000) > 1) {
        // console.log("超过100W像素");
        count = ~~(Math.sqrt(count) + 1) //计算要分成多少块瓦片
        //      计算每块瓦片的宽和高
        let nw = ~~(width / count)
        let nh = ~~(height / count)
        tCanvas.width = nw
        tCanvas.height = nh
        for (let i = 0; i < count; i++) {
            for (let j = 0; j < count; j++) {
                tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh)
                ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh)
            }
        }
    } else {
        ctx.drawImage(img, 0, 0, width, height)
    }
    // //修复ios上传图片的时候 被旋转的问题
    // if (Orientation != '' && Orientation != 1) {
    //     switch (Orientation) {
    //         case 6: //需要顺时针（向左）90度旋转
    //             this.rotateImg(img, 'left', canvas)
    //             break
    //         case 8: //需要逆时针（向右）90度旋转
    //             this.rotateImg(img, 'right', canvas)
    //             break
    //         case 3: //需要180度旋转
    //             this.rotateImg(img, 'right', canvas) //转两次
    //             this.rotateImg(img, 'right', canvas)
    //             break
    //     }
    // }
    //进行最小压缩
    let ndata = canvas.toDataURL('image/jpeg', 0.5)
    tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
    // console.log(ndata)
    return ndata
}
// 旋转图片
function rotateImg(img, direction, canvas) {
    //最小与最大旋转方向，图片旋转4次后回到原方向
    const min_step = 0
    const max_step = 3
    if (img == null) return
    //img的高度和宽度不能在img元素隐藏后获取，否则会出错
    let height = img.height
    let width = img.width
    let step = 2
    if (step == null) {
        step = min_step
    }
    if (direction == 'right') {
        step++
        //旋转到原位置，即超过最大值
        step > max_step && (step = min_step)
    } else {
        step--
        step < min_step && (step = max_step)
    }
    //旋转角度以弧度值为参数
    let degree = (step * 90 * Math.PI) / 180
    let ctx = canvas.getContext('2d')
    switch (step) {
        case 0:
            canvas.width = width
            canvas.height = height
            ctx.drawImage(img, 0, 0)
            break
        case 1:
            canvas.width = height
            canvas.height = width
            ctx.rotate(degree)
            ctx.drawImage(img, 0, -height)
            break
        case 2:
            canvas.width = width
            canvas.height = height
            ctx.rotate(degree)
            ctx.drawImage(img, -width, -height)
            break
        case 3:
            canvas.width = height
            canvas.height = width
            ctx.rotate(degree)
            ctx.drawImage(img, -width, 0)
            break
    }
}
//将base64转换为文件
function dataURLtoFile(dataurl,filename) {
    var arr = dataurl.split(','),
        mime = arr[0].match(/:(.*?);/)[1],
        bstr = atob(arr[1]),
        n = bstr.length,
        u8arr = new Uint8Array(n);
    while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
    }
    return new File([u8arr], filename, {
        type: mime
    });
}